1. black people slang for fighting, orginated from the dirty south and heard in crime mobbs single "knuck if you buck".
2. Is used when one homie wants to throw down torwards another homie.
3. Is commonly seen when crunked white boys who think they are black, try to dance and get down.

(1.homie):Yo nigga!
(2.homie):what?
(1.homie):KNUCK IF YOU BUCK!
(homie 1 & 2): KNUCK IF YOU BUCK BOY! KNUCK IF YOU BUCK BOY!KNUCK IF BUCK! KNUCK IF YOU BUCK!